Turbocharged engines often employ bypass mechanisms, also known as wastegates, to regulate a turbocharger speed and a resulting boost pressure of air delivered to an intake of the engine. A bypass mechanism typically employs at least one valve to seal exhaust gas within the primary exhaust manifold until the valve is opened to allow a portion of the exhaust to bypass the turbo machinery. The valve position can be varied to control the amount of energy released from the primary exhaust stream.
Valves of sufficient size to allow passage of the required mass flow of exhaust energy typically consume a rather large volume of space between the exhaust manifold and the turbocharger package, as does the ducting required to release the energy to an exhaust manifold downstream of the turbocharger. Further, if the bypass mechanism exhausts to an emissions aftertreatment component with multiple intakes, distributing the flow evenly between the intakes can present a challenge. Further, some valve configurations tend to create flow distortion, especially at small openings that prevents uniform distribution of the exhaust gas even far downstream from the valve.
One example of a turbocharger bypass mechanism is described in U.S. Pat. No. 3,104,520, which issued to Cazier et al. on Sep. 24, 1963 (“the '520 patent”). The '520 reference discloses a turbocharger system that includes a spring-biased valve that may be opened and closed to selectively cause exhaust gas to bypass a turbine of the turbocharger. In particular, the valve is configured to open a bypass passage that delivers the exhaust gas to an exhaust pipe. The bypass passage is a narrow, elongated passageway.
The bypass mechanism of the '520 patent suffers from several drawbacks. In particular, the use of a single valve for controlling the flow of exhaust into the bypass passage limits the amount of control over the amount and flow rate of the exhaust. Further, the narrow, elongated passageway may experience rapid changes in temperature that may lead to degradation and/or damage to certain portions of the passageway. In addition, the bypass mechanism of the '520 patent takes up a large amount of space in order to reroute the bypassed exhaust gas to the exhaust pipe.
The present disclosure is directed at overcoming one or more of the shortcomings set forth above and/or other problems of the prior art.